1. Field of the Invention
The present invention relates to an apparatus for feeding glass batch materials into a glass melting furnace. More particularly, it relates to an improved blanket feeder type feeding apparatus.
2. Description of the Prior Art
The glass batch materials can be granular materials of a mixture of various glass forming materials which can be further mixed with glass cullet.
Various type apparatuses have been proposed as the apparatus for feeding the glass batch materials into the glass melting furnace. The typical type feeders i.e. a blanket feeder and a screw feeder have been mainly used.
In the case of the blanket feeder, a mixture of the glass batch materials is intermittently fed in the form of thin layer having wide width on the molten glass at the charging area in the glass melting furnace, through a feeding trough or plate which is reciprocally moved, as disclosed in U.S. Pat. No. 2,281,050.
In the case of the screw feeder, a mixture of the glass batch materials is continuously extruded in the form of narrow layer from a hopper onto the molten glass through a screw or a spiral propeller blade disposed in a cylindrical feed chamber, as disclosed in U.S. Pat. No. 1,906,695.
The blanket feeder has significantly high heat receiving efficiency of the glass batch materials in the melting furnace, high stability of the condition of the glass batch layer and high stability of the molten glass flow in the furnace in comparison with those of the screw feeder.
Thus, it has been considered that a melting capacity, a product quality and a thermal efficiency of the blanket feeder are respectively superior to those of the screw feeder.
Recently, the blanket feeder has been mainly used in large size tank furnace such as the glass melting furnace for manfacturing a sheet or flat glass. However, the advantageous effect of the screw feeder is to be capable of separating the atmosphere in the glass melting furnace from the outer atmosphere in the operation for feeding the glass batch materials.
Sometimes, the glass forming materials used for preparing the optical glass, the electron tube glass, the lamp glass and the cathode-ray tube glass may contain toxic or volatile materials such as lead, arsenic or boron component which poison the sanitary environment except those of the ordinary soda lime glass.
In the melting of glass containing the toxic components, the dust, mist and gas containing the toxic or volatile materials are formed in the melting furnace. It is important from the sanitary environment to carry out an operation so as to prevent the toxic materials to leak from the gap between the glass batch material feeding apparatus and the furnace structure near the charging inlet of the melting furance. It is obliged to use the screw feeder having excellent sealing effect in the melting of the glass containing the toxic materials even though the melting capacity is decreased.
In the sanitary view, it is important to consider a problem of the leakage of toxic gas components such as sulfur oxides and nitrogen oxides which are formed in the glass melting furnace when the heavy oil is burnt to melt the glass as well as to consider the environment of the furnace containing the specific toxic materials such as lead, arsenic etc.
The blanket feeder type glass batch material feeding apparatus having a function for preventing the leakage of the atmosphere of the furnace has not been developed.
One difficulty encountered in the practical use of the blanket feeder is to drop the glass batch materials from the sliding part of the trough since the glass batch materials is fed by reciprocal movement of the feeding trough. The increase of the concentration of dust in the working place caused by the fallen glass batch materials is unfavorable from the viewpoint of the sanitary environment and the maintenance of the apparatus.